Robotic vehicle

ABSTRACT

A robotic vehicle is disclosed, which is characterized by high mobility, adaptability, and the capability of being remotely controlled in hazardous environments. The robotic vehicle includes a chassis having front and rear ends and supported on right and left driven tracks. Right and left elongated flippers are disposed on corresponding sides of the chassis and operable to pivot. A linkage connects a payload deck, configured to support a removable functional payload, to the chassis. The linkage has a first end rotatably connected to the chassis at a first pivot, and a second end rotatably connected to the deck at a second pivot. Both of the first and second pivots include independently controllable pivot drivers operable to rotatably position their corresponding pivots to control both fore-aft position and pitch orientation of the payload deck with respect to the chassis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. patent application claims priority under 35 U.S.C. §119(e) toU.S. Provisional Application 60/828,606, filed on Oct. 10, 2006, U.S.Provisional Application 60/942,598, filed on Jun. 7, 2007, U.S.Provisional Application 60/878,877, filed on Jan. 5, 2007, and U.S.provisional patent application 60/908,782, filed on Mar. 29, 2007. Thedisclosures of the aforementioned prior applications are herebyincorporated by reference in their entireties and are thereforeconsidered part of the disclosure of this application.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

This invention was in part with Government support under contractN41756-06-C-5512 awarded by the Technical Support Working Group of theDepartment of Defense. The Government may have certain rights in theinvention.

TECHNICAL FIELD

This disclosure relates to robotic vehicles.

BACKGROUND

A new generation of robotic systems and tools is required to meet theincreasing terrorist threat in the US and abroad. The lack ofadaptability and limited capability of existing remote controlledsystems available to Hazardous/First Response/Explosive OrdnanceDisposal (EOD) teams has frustrated many teams worldwide. The unique andoften dangerous tasks associated with the first responder missionrequire personnel to make quick decisions and often adapt their tools inthe field to combat a variety of threats. The tools must be readilyavailable, robust, and yet still provide surgical precision whenrequired.

Robots for versatile tasks potentially may be built in any reasonablesize. Known production robots are usually in the 40-100 lb. range, whichmay be carried by an infantryman at the low end and by a utility vehicleat the upper end. Production robots are different from researchrobots—practical considerations outweigh theoretical capabilities.Robots of increased size have been proposed, but as they become larger,necessary capabilities compete with one another. Size and weight arelimited by deployment and power/refueling/battery life constraints.Minimum size and weight are limited by the necessity of carrying usefulpayloads, and again, power/refueling/battery life constraints. Theeffects of the square-cube law complicate the necessary balance, becausethe volume or weight often grows with the cube of the size increase.

SUMMARY

In one aspect, a skid steer drive includes a drive wheel and a firstvolume within the skid steer drive adjacent the drive wheel. The skidsteer drive includes a load shifting assembly including a tilt motor,and having a second volume within the load shifting assembly adjacentthe tilt motor. The skid steer drive includes a chassis having a thirdvolume within the chassis adjacent the drive wheel; and at least threesets of motive power elements, among them a battery assembly, main drivemotor assembly, and load shifting motor assembly, the three sets ofmotive power elements being distributed among the first volume, secondvolume, and third volume.

In another aspect, a mobile robot includes a skid steer drive having adrive wheel and a first volume within the skid steer drive adjacent thedrive wheel. The mobile robot includes a load shifting assemblyincluding a load tilting motor and a load shifting motor, and having asecond volume within the load shifting assembly adjacent the loadtilting motor. The mobile robot includes a chassis having a third volumewithin the chassis adjacent the drive wheel, and a through space intowhich the load shifting assembly may seat itself, and a main drive motoramplifier and load shifting motor amplifier located in the first volume,a battery assembly being located in the second volume, and a main drivemotor and the load shifting motor being located in the third volume.

In yet another aspect, a mobile robot includes a skid steer drive havinga drive wheel and a first volume within the skid steer drive adjacentthe drive wheel and a load shifting assembly having a second volumetherewithin. The mobile robot includes a chassis having a third volumewithin the chassis adjacent the drive wheel, and a through space intowhich the load shifting assembly may seat itself. The mobile robot alsoincludes a main drive motor amplifier being located in the first volume,a battery assembly and the load tilting motor located in the secondvolume so that the battery assembly tilts together with the loadshifting assembly, and a main drive motor being located in the thirdvolume.

In yet another aspect, an environmentally sealed mobile robot includes askid steer drive having a first volume therewithin and a cast unitaryload shifting assembly having a second volume therewithin. The mobilerobot includes a cast unitary chassis having a third volume adjacent theskid steer drive internally connected via a passage to a fourth volumeadjacent the first volume. The mobile robot also includes a sealedhollow linkage connecting the second volume and the third volume. Themobile robot includes a main drive motor amplifier being sealed into thefirst volume and fourth volume and powering a main drive motor in thethird volume via the passage, a battery assembly and the load tiltingmotor being sealed into second volume so that the battery assembly tiltstogether with the load shifting assembly and the battery powers the maindrive motor amplifier and main drive motor via the sealed hollowlinkage.

In another aspect, a mobile robot includes a tracked drive having adrive wheel and a first volume within the envelope of the tracked driveand a load shifting assembly having a second volume therewithin. Themobile robot also includes a chassis into which the first volumeextends, and having a third volume therewithin adjacent the drive wheel.The first volume housing a motor amplifier that sinks heat via thechassis, the second volume housing a battery assembly and load tiltingmotor assembly that sink heat via the load shifting assembly; and thethird volume housing drive motors that sink heat via the chassis.

According to another aspect of the disclosure, a robotic vehicleincludes a chassis having front and rear ends and supported on right andleft driven tracks, each track trained about a corresponding front wheelrotatable about a front wheel axis. Right and left elongated flippersare disposed on corresponding sides of the chassis and operable to pivotabout the front wheel axis of the chassis, each flipper having a driventrack about its perimeter. A linkage connects a payload deck assembly,configured to support a functional, securely mounted and integratedpayload (in some cases, modular payloads, unconnected payloads and/orfunctional payload), to the chassis. The linkage has a first endrotatably connected to the chassis at a first pivot, and a second endrotatably connected to the deck at a second pivot. Both of the first andsecond pivots include independently controllable pivot drivers operableto rotatably position their corresponding pivots to control bothfore-aft position (as well as vertical position, the pivots beinginterconnected by a linkage that makes a swept motion) and pitchorientation of the payload deck assembly with respect to the chassis. Inone example, the first pivot is rotatable through an angle of at least180 degrees. The first pivot is not necessarily limited by a range ofmotion of the pivot, but rather by those positions in which the linkage,deck assembly, or payload interfere with part of the robot such as thechassis or with the ground—which may depend on the character of theground and pose of the robot. Accordingly, in another implementation,the sweep of the linkage is limited by the chassis of the robot, whichis configured as small tube element connecting chassis arms. The deckassembly and linkage may sweep between the chassis arms and between theflippers in either direction, and may sweep past a horizontal linedefined by one chassis track wheel and bogey, in either direction foreor aft of the pivot. In another implementation, the sweep is limited to74 degrees to improve stability and shock resistance on open ground. Ineach case, the payload deck assembly, with or without payload(s), may betilted to move the center of gravity of the robot further in a desireddirection. The linkage may comprise two parallel links spaced apartlaterally.

The independently controllable pivot drivers provide both fore-aftposition (and a wide sweep range) and pitch orientation of the payloaddeck assembly with respect to the chassis to selectively displace acenter of gravity of the payload deck assembly both forward and rearwardof a center of gravity of the chassis. This provides enhanced mobilityto negotiate obstacles. Hereinafter, center of gravity or center of massmay be abbreviated “CG.”

Rotation of the linkage about its first and second pivots enablesselective positioning of a center of gravity or center of mass of thepayload deck assembly both fore and aft the front wheel axis as well asboth fore and aft of a center of gravity of the chassis. In oneimplementation, the first pivot of the linkage is located above andforward of the front wheel axis and swings the linkage for displacingthe center of gravity of the payload deck assembly to a desiredlocation. Furthermore, when the first end of the linkage is rotatablyconnected near the front of the chassis, the payload deck assembly isdisplaceable to an aftmost position in which the payload deck assemblyis located within a footprint of the chassis.

In one example, the payload deck assembly includes connection points forboth a functional payload power link and a functional payloadcommunication link, which may comprise an Ethernet link. In oneimplementation, the functional payload communication link is a packetswitched network connectable to a distribution switch or router.

The payload deck assembly includes an electronics bin (also “CG tub”)which holds most of the electronics of the robot (as well as the uppermotor(s) for tilting the paylaod deck assembly, but excepting motorcontrol and drivers for the drive motors, which is housed in thechassis), and supports a dockable battery unit slid into the bottom ofthe electronics bin as well as a accepting a modular payload deck, whichdefines threaded holes to accept functional payloads and includesmultiple functional payload connection pads positioned to accommodateselective connection of multiple functional payload units to the payloaddeck. Each connection pad includes connection points for both functionalpayload power and functional payload communication (as well assufficient hard points nearby for such payloads to be secured to thedeck with sufficient fasteners to reliably secure the mass of thepayload through tilting operations of the deck). The payload deck canaccept as a payload unit a removable radio receiver unit (which cancommunicate with a remote controller unit) operably connected to a drivesystem of the chassis. A battery unit is also removable secured to thebottom of the deck, so as to place the significant weight of batteriesas low as possible in the mass that is used for shifting the center ofgravity of the vehicle. In one example, the payload deck constitutesbetween about 30 and 50 percent of a total weight of the vehicle. Thepayload deck may also accept an Ethernet camera as a payload unit.

In one implementation, the payload deck further accepts as payload unitsremovable sensor units. The sensor may be, for example, infrared,chemical, toxic, light, noise, and weapons detection.

The left and right flippers comprise elongated members, wherein flippertracks are trained about corresponding rear wheels independentlyrotatable about the front wheel axis.

The robotic vehicle can climb a step by using the independentlycontrollable pivot drivers to control both sweep and pitch orientationof the payload deck assembly with respect to the chassis to selectivelydisplace the center of gravity of the payload deck assembly the bothforward and rearward of the center of gravity of the chassis. Therobotic vehicle may initiates a step climb by pivoting the first andsecond flippers upward to engage the edge of the step. Differentobstacles can be accommodated by different strategies that use the fullrange of the sweepable and tiltable CG of the entire payload deckassembly, or of the payload deck assembly when combined with a payload.An advantage of the disclosed system is that the addition of payloadweight on the payload deck assembly increases the flexibility andmobility of the robot with respect to surmounting obstacles of variousshapes. The robotic vehicle also positions the center of gravity of thepayload deck assembly above the front end of the chassis. Next, therobotic vehicle pivots the first and second flippers downward on theedge of the step to engage the top of the step and drives forward. Therobotic vehicle continues to displace the center of gravity of thepayload deck assembly beyond the front of the chassis by rotating boththe first and second pivots. As shown in FIG. 14, tilting the deckassembly further advances the center of gravity of the entire vehicle.Finally, the robotic vehicle drives forward to pull the chassis over theedge of the step.

In another aspect of the disclosure, a skid steered robot includes achassis supporting a skid steered drive and a set of driven flippers,each flipper being pivotable about a first pivot axis common with adrive axis of the chassis. A linkage substantially at the leading end ofthe chassis is pivotable about a second pivot axis. A deck assembly ispivotable about a third pivot axis substantially at a distal end of thelinkage. The deck assembly includes a power supply, a packet networkconnection, a modular deck support structure; and a modular deck. Themodular deck includes a deck mount which fits the modular deck supportstructure and at least two externally available common connectors. Atleast one of the deck assembly or modular deck includes a power supplyswitching circuit that switches available power from the power supplybetween the at least two common connectors, and a network switch thatswitches packet network traffic between the at least two commonconnectors.

In another aspect of the disclosure, a skid steered robot includes a setof driven flippers, each flipper being pivotable about a first pivotaxis common with a drive axis of the chassis. A deck assembly, disposedabove the chassis, includes a power supply, a packet network connection,a modular deck support structure, a deck wiring harness connectorincluding packet network cabling and power cabling, and a modular deck.The modular deck includes a deck mount which fits the modular decksupport structure, at least two externally available common connectors,a power supply switching circuit that switches available power from thepower supply between at least two common connectors, a network switchthat switches packet network traffic between the at least two commonconnectors, and a deck wiring harness that connects to the deck wiringharness connector and carries power and network to and from the modulardeck.

In another aspect of the disclosure, a modular deck for a roboticvehicle includes a base configured to be secured to the vehicle, whereinthe base receives both a power link and a communication link from therobotic vehicle. A platform configured to support a removable functionalpayload is secured to the base and has at least one connection point forboth a functional payload power link and a functional payloadcommunication link. The connection point is linked to both the basepower link and the base communication link.

In one aspect, a robotic vehicle includes a chassis having front andrear ends, an electric power source supported by the chassis, andmultiple drive assemblies supporting the chassis. Each drive assemblyincludes a track trained about a corresponding drive wheel and a drivecontrol module. The drive control module includes a drive controlhousing, a drive motor carried by the drive control housing and operableto drive the track, and a drive motor controller in communication withthe drive motor. The drive control module may further include aback-drivable gearbox coupling the motor to the track. The drive motorcontroller includes a signal processor and an amplifier commutator incommunication with the drive motor and the signal processor and iscapable of delivering both amplified and reduced power to the drivemotor from the power source. The drive control module may communicatewith a robot controller over a controller area network bus.

In one implementation, the drive motor controller further comprises ahealth monitor for monitoring the proper functioning of the signalprocessor and the amplifier commutator. The health monitor sends asignal to the amplifier commutator to cease operation of the motor upondetecting a malfunction. In one instance, the amplifier commutatorincludes a commutator in communication with the drive motor, a DC/DCconverter capable of delivering both amplified and reduced power to thecommutator, and a programmable logic circuit in communication with thesignal processor, DC/DC converter, and commutator.

In another implementation, the drive control module also includesmultiple magnetic field sensors mounted radially about to the motor todetect magnetic pulses, a velocity sensor connected to the motor, and arotary position sensor connected to the motor. The signal processorcomprises logic for three cascading control loops comprising motorcurrent, motor voltage, and motor rotor rotation. The current controlloop of the signal processor includes reading a current feedback fromthe commutator, reading the magnetic field sensors, computing apulse-width modulation output, writing the pulse-width modulation outputto a shared structure accessible by the other control loops, andupdating a cycle counter. The voltage control loop of the signalprocessor includes reading a velocity feedback from the velocity sensor,reading a voltage feedback from the DC/DC converter, computing acommanded current based on a current limit, maximum current from athermal protection model, and a current rate of change limit, andwriting the commanded current to a shared structure accessible by theother control loops. The motor rotor rotation control loop of the signalprocessor includes reading a rotational position feedback from therotary position sensor, computing a commanded velocity based on currentand velocity limits, and writing the commanded velocity to a sharedstructure accessible by the other control loops.

In one example, the DC/DC converter receives about 42 V from the powersource and is capable of delivering between about 0 V and about 150 V.The power source may include three 14 V batteries in series and three 14V batteries in parallel, providing about 42 V.

In another example, the drive control module is separately andindependently removable from a receptacle of the chassis as a completeunit. The drive control module is also sealed within the receptacle ofthe chassis from an outside environment and passively cooled by thechassis.

In another aspect, a robotic vehicle includes a chassis having front andrear ends and is supported on right and left driven drive tracks. Eachdrive track is trained about a corresponding front wheel rotatable abouta front wheel axis. Right and left elongated flippers are disposed oncorresponding sides of the chassis and are operable to pivot about thefront wheel axis of the chassis. Each flipper has a driven flippertrack. A flipper actuator module is supported by the chassis and isoperable to rotate the flippers. At least one drive module is supportedby the chassis and is operably connected to drive at least one of thedrive and flipper tracks. A payload deck is configured to support apayload and a linkage connects the payload deck to the chassis. Thelinkage has a first end rotatably connected to the chassis at a firstpivot and a second end rotatably connected to the deck at a secondpivot. The first and second pivots include respective linkage actuatormodules operable to rotatably position their corresponding pivots tocontrol orientation of the payload deck with respect to the chassis. Thetrack drive modules and actuator modules each include a module housing,a motor supported by the module housing, and a motor controllersupported by the module housing and in communication with the motor. Thelinkage actuator modules are each separately and independently removableas complete units. Also, the track drive modules and the flipperactuator module are each separately and independently removable fromrespective receptacles of the chassis as complete units. In someexamples, the actuator modules are each interchangeable and the trackdrive modules are each interchangeable. Furthermore, the track drivemodules and the flipper actuator module may each be sealed within theirrespective receptacles of the chassis from an outside environment andpassively cooled by the chassis.

In some examples, the track drive modules and actuator modules may eachcommunicate with a robot controller over a controller area network bus.The track drive modules and actuator modules may also include aback-drivable gearbox supported by the module housing and coupled to themotor. Furthermore, the actuator modules may include a slip clutchsupported by the module housing and coupled to a planetary gearbox. Inone example, the motor of the actuator module provides magnetic brakinginhibiting actuation upon power loss.

In one implementation, the motor controller includes a signal processorand an amplifier commutator in communication with the drive motor andthe signal processor. The amplifier commutator is capable of deliveringboth amplified and reduced power to the drive motor.

In another implementation, each module includes a power connectordisposed on an outer surface of the module housing and configured tomate with a corresponding power bus connector to establish an electricpower connection to the module. Each track drive module establishes anelectric power connection with the bus power connector within itsrespective receptacle as the module is placed within the receptacle.

In yet another aspect, a method of controlling a robotic vehicleincludes providing a robotic vehicle that includes a chassis havingfront and rear ends, at least one electric power source supported by thechassis, and a drive assembly supporting the chassis and driven by adrive control module. The drive control module includes a drive controlhousing, a drive motor carried by the drive control housing and operableto drive the drive assembly, and a drive motor controller incommunication with the drive motor. The drive motor controller includesa signal processor and an amplifier commutator in communication with thedrive motor and the signal processor. The method also includes providinga robot controller with a power management control logic that recognizesa power source type and monitors an available power level. The robotcontroller communicates drive commands to the signal processors of eachdrive control module based on the power source type and the availablepower level. In one example, the power management control logic monitorsa power source temperature as well. Accordingly, the robot controllercommunicates to the signal processors of each drive control module,delivering drive commands based on the power source temperature.

In one implementation, the signal processor of the drive motorcontroller checks for regenerative braking, where upon regenerativebraking, the signal processor checks the available power level of thepower source and charges the power source until a charged level isattained or regenerative breaking ends.

The robotic vehicle may also include a payload deck supported by thechassis. The payload deck is configured to receive at least one electricpower source and includes a payload deck signal processor supported bythe payload deck. The payload deck signal processor recognizes a powersource type, monitors an available power level, and communicates thepower source type and available power level of the at least one electricpower source to the robot controller. The payload deck signal processormay communicate with the robot controller over a controller area networkbus.

In one example, the robotic vehicle includes a linkage connecting thepayload deck to the chassis, the linkage having a first end rotatablyconnected to the chassis at a first pivot, and a second end rotatablyconnected to the deck at a second pivot. The first and second pivotsinclude respective linkage actuator modules operable to rotatablyposition their corresponding pivots to control orientation of thepayload deck with respect to the chassis. The actuator modules eachinclude an actuator module housing, an actuator motor supported by themodule housing, and an actuator motor controller supported by the modulehousing and in communication with the actuator motor. The actuator motorcontroller includes a signal processor, an amplifier commutator incommunication with the actuator motor and the signal processor, and aslip clutch supported by the module housing and coupling the actuatormotor to the respective pivot.

In one instance, the signal processor of the actuator motor controllerchecks for regenerative impact absorption, such as when the slip clutchabsorbs recoil of the payload deck. Upon regenerative impact absorption,the signal processor of the actuator motor controller checks theavailable power level of the power source and charges the power sourceuntil a charged level is attained or regenerative absorption ends.

The details of one or more implementations of the invention are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the invention will be apparent fromthe description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a robotic vehicle.

FIG. 2 is an exploded view of the robotic vehicle.

FIG. 3 is a front view of the robotic vehicle.

FIG. 4 is a back view of the robotic vehicle.

FIG. 5 is a top view of the robotic vehicle.

FIG. 6 is a bottom view of the robotic vehicle.

FIG. 7 is an exploded perspective view of the robotic vehicle.

FIG. 8 is a side view of the robotic vehicle.

FIG. 9 is an side view of the robotic vehicle.

FIG. 10 is a perspective view of a payload deck for a robotic vehicle.

FIG. 11 is a perspective view of a payload deck for a robotic vehicle.

FIG. 12 is a perspective view of a payload deck for a robotic vehicle.

FIG. 13 is a perspective view of the robotic vehicle with a manipulatorarm.

FIGS. 14-17 are side views of a robotic vehicle climbing.

FIGS. 18-21 are side views of a robotic vehicle climbing.

FIG. 22 is a side view of a robotic vehicle climbing stairs.

FIG. 23 is a front view of a robotic vehicle traversing an incline.

FIG. 24 is a perspective view of a robotic vehicle in a neutral posture.

FIG. 25 is a perspective view of a robotic vehicle in a standingposture.

FIG. 26 is a perspective view of a robotic vehicle in a kneelingposture.

FIG. 27 is a perspective view of a robotic vehicle in a kneelingposture.

FIG. 28 is a side view of a robotic vehicle.

FIG. 29 is a partially exploded view of a large skid-steered roboticvehicle.

FIG. 30 is a schematic side view of a large skid-steered roboticvehicle.

FIG. 31 is a schematic top view of a large skid-steered robotic vehicle.

FIG. 32 is a schematic side view of a large skid-steered roboticvehicle.

FIG. 33 is a schematic top view of a large skid-steered robotic vehicle.

FIG. 34 is a schematic side view of a large skid-steered roboticvehicle.

FIG. 35 is a schematic top view of a large skid-steered robotic vehicle.

FIG. 36 is a schematic view of a robotic vehicle.

FIG. 37A is a top view of a drive module.

FIG. 37B is a bottom view of a drive module.

FIG. 37C is a sectional view of a drive module.

FIG. 37D is an exploded view of a drive module.

FIG. 38A is a perspective view of an actuator module.

FIG. 38B is an exploded view of an actuator module.

FIG. 39A is a schematic view of a drive module.

FIG. 39B is a schematic view of a DC/DC converter.

FIG. 39C is a schematic view of a DC/DC converter.

FIG. 39D is a schematic view of a commutator.

FIG. 39E is a schematic view of control logic for a digital signalprocessor.

FIG. 39F is a motor current direction state diagram.

FIG. 39G is a current control loop mode diagram.

FIG. 39H is a schematic view of control logic for a digital signalprocessor.

FIGS. 40A and 40B together is a schematic view of a drive module.

FIG. 41 is a schematic view of control logic.

FIG. 42 is a schematic view of a robotic vehicle mission.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIG. 1, a robotic vehicle 10, in one implementation, is aremotely operated vehicle that enables the performance of manpowerintensive or high-risk functions (i.e., explosive ordnance disposal;urban intelligence, surveillance, and reconnaissance (ISR) missions;minefield and obstacle reduction; chemical/toxic industrial chemicals(TIC)/toxic industrial materials (TIM); etc.) without exposing operatorsdirectly to a hazard. These functions often require the robotic vehicle10 to drive quickly out to a location, perform a task, and either returnquickly or tow something back. The robotic vehicle 10 is operable from astationary position, on the move, and in various environments andconditions.

Referring to FIGS. 1-6, a robotic vehicle 10 includes a chassis 20 thatis supported on right and left drive track assemblies, 30 and 40respectively, having driven tracks, 34 and 44 respectively. Each driventrack 34, 44, is trained about a corresponding front wheel, 32 and 42respectively, which rotates about front wheel axis 15. Right and leftflippers 50 and 60 are disposed on corresponding sides of the chassis 20and are operable to pivot about the front wheel axis 15 of the chassis20. Each flipper 50, 60 has a driven track, 54 and 64 respectively,about its perimeter that is trained about a corresponding rear wheel, 52and 62 respectively, which rotates about the front wheel axis 15.

Referring to FIG. 7, in one implementation, the robotic vehicle 10includes right and left motor drivers, 36 and 46, driving correspondingdrive tracks, 34 and 44, and flipper tracks, 54 and 64, which aresupported between their front and rear ends by bogie wheels 28. Aflipper actuator module 55 is supported by the chassis 20 and isoperable to rotate the flippers, 50 and 60. In one example, the flippers50, 60 are actuated in unison. In other examples, the flippers 50, 60are actuated independently by right and left flipper actuators 55.

Referring to FIG. 8, a linkage 70 connects the payload deck assembly 80to the chassis 20. The linkage 70 has a first end 70A rotatablyconnected to the chassis 20 at a first pivot 71, and a second end 70Brotatably connected to the payload deck 80 at a second pivot 73. Both ofthe first and second pivots, 71 and 73 respectively, include respectiveindependently controllable pivot drivers, 72 and 74, operable torotatably position their corresponding pivots to control both fore-aftposition and pitch orientation of the payload deck assembly 80 withrespect to the chassis 20. As shown in FIGS. 1-2, the linkage 70 maycomprise two parallel links spaced apart laterally.

Referring to FIG. 9, the first end 70A of the linkage 70 is rotatablyconnected near the front of the chassis 20 such that the payload deckassembly 80 is displaceable to an aftmost position in which the payloaddeck assembly 80 is located within a footprint of the chassis 20.Furthermore, as shown in FIGS. 1-2, the first pivot 71 of the linkage 70is located above and forward of the front wheel axis 15. The first pivot71 is rotatable through an angle of at least 180 degrees (optionally, 74degrees), in one example. Rotation of the linkage 70 about its first andsecond pivots, 71 and 73 respectively, enables selective positioning ofcenter of gravity 410 of payload deck assembly 80 both fore and aftfront wheel axis 15 as well as both fore and aft a center of gravity 400of the chassis 20. In another example, the independently controllablepivot drivers 72, 74 provide both fore-aft position (as part of sweep)and pitch orientation of the payload deck assembly 80 with respect tothe chassis 20 to selectively displace the center of gravity 410 of thepayload deck assembly 80 both forward and rearward of the center ofgravity 400 of the chassis 20, displacing a center of gravity 450 of theentire robot 10.

The robotic vehicle 10 is electrically powered (e.g. a bank of ninestandard military BB-2590 replaceable and rechargeable lithium-ionbatteries). Referring to FIGS. 2-3, the payload deck assembly 80,specifically the electronics tub 90, accommodates a slidable, removablebattery unit 92. Skid pad 94, as shown in FIG. 6, may be secured to thebottom of the battery unit 92 to protect the battery 92 and aidmanageability. The payload deck assembly 80 may carry an additionalbattery supply on one of the selectable connection pads 810, increasingthe available power capacity (e.g. an additional bank of nine batteriesmay be carried on payload deck).

Referring again to FIGS. 2-6, a payload deck assembly 80, including anelectronics bin 90 and payload deck 806 (D1, D2, D3 in other drawingsherein), is configured to support a removable functional payload 500.FIGS. 3-4 illustrate the robotic vehicle 10 with the payload deckassembly 80 including front and rear functional payload powerconnectors, 200 and 210, and a user interface panel 220. FIG. 2illustrates one example where the payload deck assembly 80 includesfront and rear sensor pods, 240 and 250 respectively. In someimplementations, the sensor pods 240, 250 provide infrared, chemical,toxic, light, noise, and weapons detection, as well as other types ofsensors and detection systems. A primary driving sensor may be housed ina separate audio/camera sensor module mounted to the payload deckassembly 80 that contains at least one visible spectrum camera. Audiodetection and generation is realized using an audio/camera sensor modulemounted to the payload deck assembly 80, in one example.

In some implementations, robotic vehicle 10 tows a trailer connected torear payload connector 290, as shown in FIG. 5. Exemplary payloads forthe trailer include a small generator, which significantly extends bothrange and mission duration of robotic vehicle, field equipment, andadditional functional payload units 500 attachable to the payload deckassembly 80.

The payload deck assembly 80 accepts the mounting of one or morefunctional payload modules 500 that may include robotic arms, chemical,biological and radiation detectors, and a sample container. The roboticvehicle 10 automatically detects the presence and type of an installedfunctional payload 500 upon start-up. Referring to FIG. 5, the payloaddeck 806 defines threaded holes 808 to accept a functional payload 500.FIG. 5 also illustrates one or more functional payload connection pads810 positioned on the payload deck assembly 80 to accommodate selectiveconnection of multiple functional payload units 500. Each functionalpayload connection pad 810 delivers power, ground and communications toa functional payload unit 500. For example, robotic vehicle 10 mayprovide up to 300 W (threshold), 500 W (goal) of power to a payload 500at 42V, up to 18 A. The communication link may include Ethernet linkcommunications. In one example, payload deck assembly 80 constitutesbetween about 30 and 70 percent of the vehicle's total weight. Thepayload deck assembly 80 further includes a removable controller unit350 operably connected to a drive system (e.g. the motor drivers 36, 46)of the chassis 20. The robotic vehicle 10 communicates with an operatorcontrol unit (OCU) through optional communication functional payloadmodule(s) 500. The robotic vehicle 10 is capable of accepting andcommunicating with a radio functional payload module 500.

Referring to FIGS. 10-12, modular decks D1, D2, D3 are removable payloaddecks 806 modularly secured to the electronics bin 90 to form thepayload deck assembly 80. The modular decks D1, D2, D3 maintainconnectivity to functional payloads 500 located on the decks D1, D2, D3while allowing interchangeability with a payload deck assembly base 805.The modular decks D1, D2, D3 receive power and communication from a deckconnector 802 attached by a wiring harness 804. FIG. 17 depicts adevelopment deck D1 including sparsely spaced connector pads 806. FIG.18 depicts a mule deck D2 including netting 808 for carrying loads andat least one connector pad 806. FIG. 19 depicts a manipulator deck D3including an integral bracing 810 for a large manipulator arm. Theintegral bracing 810 housing at least one connector pad 806. Theconnectors pads 806 available on the decks D1, D2, D3 each carry 42V, upto 18 A power; ground; and Ethernet, for example. FET switches connectedto each connector pad 806 are overload protected and are controlled by adigital signal processor (DSP) on the deck to distribute power. The DSPis controlled via a controller area network (CAN) bus, a knownindustrial and automotive control bus.

FIG. 13 illustrates a robotic arm module 600 as a functional payload 500attached to the payload deck assembly 80. The robotic arm module 600provides full hemispherical reach (or more, limited only byinterference; or less, limited by other needs of the robot 10) aroundthe robotic vehicle 10. The robotic arm module 600 provides liftingcapacity and an additional means for shifting the robotic vehicle'scenter of gravity 450 forward, e.g. when ascending steep inclines, andrearward, e.g. for additional traction.

The robotic vehicle 10 may sense elements of balance through the linkage70 (e.g., via motor load(s), strain gauges, and piezoelectric sensors),allowing an operator or autonomous dynamic balancing routines to controlthe center of gravity 410 of the payload deck assembly 80 and the centerof gravity 430 of the linkage 70 for enhanced mobility, such as to avoidtip over while traversing difficult terrain.

FIGS. 14-17 illustrate the robotic vehicle 10 climbing a step by usingthe independently controllable pivot drivers 72 and 74 to control bothfore-aft position and pitch orientation of the payload deck assembly 80with respect to the chassis 20 to selectively displace the center ofgravity 410 of the payload deck assembly 80 both forward and rearward ofthe center of gravity 400 of the chassis 20. Referring to FIG. 14, instep S1, the robotic vehicle 10 initiates step climbing by pivoting thefirst and second flippers 50 and 60, respectively, upward to engage theedge 902 of the step 900. The robotic vehicle 10 also positions thecenter of gravity 410 of the payload deck assembly 80 above the frontend of chassis 20. Next, as shown in FIGS. 15-16, in steps S2 and S3,the robotic vehicle 10 pivots the first and second flippers 50 and 60downward on the edge 902 of the step 900 to engage the top 904 of thestep and drives forward. In FIG. 15, illustrating step S2, the payloaddeck assembly 80 is further tilted to advance the center of gravity 450of the robot 10 (permitting higher obstacles to be climbed). In step S3,the robotic vehicle 10 continues to displace the center of gravity 410of the payload deck assembly 80 beyond the front of the chassis 20, asshown in FIG. 16, by rotating both the first and second pivots, 71 and73 respectively. Finally, in step S4, as shown in FIG. 17, the roboticvehicle 10 drives forward to pull the chassis 20 over the edge 902 ofthe step 900. FIGS. 18-21 illustrates the robotic vehicle 10 initiatingand completing steps S1-S4 for obstacle climbing with a functionalpayload 500 secured to the payload deck assembly 80.

In some implementations, the robotic vehicle 10 is configured tonegotiate obstacles, curbs and steps having a height of about 0.3 m (12inches), and across a horizontal gap of about 0.61 m (24 inches). Therobotic vehicle 10 has side-to-side horizontal dimensions smaller thanstandard exterior doorways (e.g. 32 inches) and interior doors (e.g. 30inches). Referring to FIGS. 22-23, the robotic vehicle 10 is configuredas to ascend and descend a flight of stairs having up to a climb angle,β, of about 37 degrees, as well as climb and descend an inclined slope,including stopping and starting, on a hard dry surface slope angle, β,of about 50 degrees. Similarly, the robotic vehicle 10 is physicallyconfigured as described herein to climb and descend, including stoppingand starting, an inclined grass covered slope having an angle, β, ofabout 35 degree grade. The robotic vehicle 10 is configured to laterallytraverse, including stopping and starting, on a grass slope angle, φ, ofabout 30 degrees. Furthermore, the robotic vehicle 10 is configured tomaneuver in standing water (fresh/sewage) having a depth of about 0.3 m(12 inches) and maintain a speed of about 20 kph (12 mph) on a pavedsurface, and about 8 kph (5 mph) through sand and mud.

The robotic vehicle 10 supports assisted teleoperation behavior, whichprevents the operator from hitting obstacles while using on boardobstacle detection/obstacle avoidance (ODOA) sensors and responsive ODOAbehaviors (turn away; turn around; stop before obstacle). The roboticvehicle 10 assumes a stair climbing pose, as illustrated in FIG. 13, ora descending preparation pose (similar to the pose shown in FIG. 13, butwith the flippers 50, 60 pointing downward) when a stair climbing orstair descending assist behavior is activated, respectively. The roboticvehicle 10 stair climbing behaviors can be configured to control (tilt)the flippers 50, 60 and control the position of the center of gravityshifter 70 as the robot 10 negotiates stairs. A stair climbing assistbehavior keeps the robotic vehicle 10 on a straight path up stairs and,in one example, may maintain a roll angle of about zero degrees.

The robotic vehicle's 10 control software provides autonomouscapabilities that include debris field mapping, obstacle avoidance, andGPS waypoint navigation. The robotic vehicle 10 can determine positionvia a global positioning system (GPS) receiver, housed in a separatesensor module 500.

The robotic vehicle 10 is fully operational after exposure to atemperature range of about −40° C. to about 71° C. (−40° F. to 160° F.)in a non-operating mode and is fully operational in a temperature rangeof about −32° C. to about 60° C. (−26° F. to 140° F.). The roboticvehicle operates during and after exposure to relative humidity up toabout 80 percent, in varied weather conditions. The robotic vehicle 10also operates during and after exposure to blowing sand and/or rain,freezing rain/ice, and in snowfall up to about 0.1 m (4 inches) indepth.

Referring to FIGS. 24-28, the robotic vehicle 10 may exhibit a varietyof postures or poses to perform tasks and negotiate obstacles. Thelinkage 70 together with the deck assembly 80, chassis 20, and flippers50, 60 all move to attain a number of standing postures. FIG. 24 depictsrobotic vehicle 10 in a neutral posture. FIG. 25 depicts the roboticvehicle 10 in one standing posture wherein the distal end of flippers 50and 60 approaches the leading end of the chassis 20 to form an acuteangle between the flippers 50 and 60 and the chassis 20. The linkage 70is entirely above a common axis 15 of the flippers 50 and 60 and thechassis 20. In one example, the deck assembly 80 tilts independentlywith respect to the robotic vehicle 10. The acute angle achieved betweenthe flippers 50 and 60 and the chassis 20 varies the standing positionswithout changing the orientation of the deck assembly 80 with respect tothe ground. In some examples, the linkage 70 is positionable at leastparallel to an imaginary line between the distal and pivot ends offlippers 50 and 60. In additional examples, the second end 70B of thelinkage 70 is positionable below an imaginary line between the distaland pivot ends of flippers 50 and 60. In another implementation, thelinkage 70 together with the deck assembly 80, chassis 20, and flippers50 and 60 can move to attain a first kneeling position, as shown in FIG.26, and a second kneeling position, as shown in FIG. 27.

FIG. 28 illustrates an implementation of centers of gravity of a roboticvehicle 1000 and distances between them. The locations of the centers ofgravity within the chassis 20, deck 80, linkage 70, and flippers 50 and60 and with respect to each other individually may be varied to attain anumber of advantages in terms of maneuverability and the ability toperform certain tasks.

There are several advantages to the present “two-bar” linkage 70 (havingindependent, powered pivots 71, 73 at the deck assembly end 70B and thechassis end 70A of the linkage 70) with respect to other structures forshifting a center of gravity.

For example, a robot equipped with a “two-bar” linkage 70 can scalehigher obstacles relative to a robot without such a linkage. In order todo so, the deck assembly 80 is tilted and/or pivoted further forward,moving the overall center of gravity 450 higher and farther forward. Arobot equipped with the two-bar linkage 70 can scale higher obstacleswhen bearing a payload 500 on top of the deck assembly 80 than without apayload 500. A high, heavy payload 500 can be tipped with the two-barlinkage 70 to provide a more pronounced shift of the center of gravity450 forward than an empty deck assembly 80. The two bar linkage 70 mayraise the deck assembly 80 and an attached a sensor pod module 500higher in a standing position, as shown in FIG. 25, even with a leveldeck, because the linkage 70 is connected at one point 73 at the top ofthe range and also at one point 71 at the bottom of the range. This isvaluable because the linkage 70 may place a sensor such as a camera,perception sensor (e.g., laser scanner) or payload sensors 500relatively higher. Other linkage systems may require connection at morethan one point, which may limit the height and/or may also tilt the deckassembly 80 at the highest position while in the standing position.

A two bar linkage 70 has a theoretical pivot range, limited only byinterference with other parts of the robot, of greater than 180 degrees.If positioned concentrically with the flipper-chassis joining axis 15,the linkage rotation range could be 360 degrees. Other constraintsdesigned herein and other advantages obtainable in other positions canchange this. For example, if the first pivot 71 of the linkage 70 ispositioned above and forward of the common chassis-flipper axis 15(e.g., about 20 mm forward and about 70 mm above), it is possible tohave a unitary structure for the chassis 20 (casting).

A straight shaft may join both flippers 50,60 directly, allowing thebottom pivoting actuator 72 to be placed off center with the flipperactuator 55. Additional pivot range past 180 degrees may be obtained, aswith additional standing height, by increasing the distance between thefirst pivot 71 and the common chassis-flipper axis 15.

Other systems may have a range of considerably less than 180 degrees,for example if the parts of such systems are limited in a pivoting ormovement range by interference among the system members. Still further,a two bar linkage has a longer effective forward extending range, sincethe linkage 70 is substantially stowable to the chassis 20. The distancebetween more than one chassis connections of the other systems mayshorten the effective forward extending range. As one additionaladvantage, a deck-side actuator 74 of the two-bar linkage 70 can be usedto “nod” (auxiliary scan) a scanning (main scanning) sensor such as a 2DLADAR or LIDAR to give a 3D depth map.

A significant problem is one of discovering or creating synergy in thedesign of the robot's functional morphology in the 200-500 lb range(e.g., 200-300 lb. plus 100-200 lbs of optional payload). There are manyfactors to balance to generate synergy, but for the purpose of thepresent discussion, the number will be limited to some directlyaffecting the shape and arrangement of the robot.

In a robot designed for sensitive environments, especially militaryrobots, electromagnetic (EM) emissions should be limited to as little aspossible. For example, EM emissions should be controlled to reduce thepossibility of triggering EM-sensitive triggers on explosive devices;and to increase the EM “stealth” of the robot.

In a robot using enough energy to move 250 lbs at reasonable speed, heatgenerated in batteries, motors, motor drivers/amplifiers, andhigh-stress mechanicals must be safely and effectively dispersed.Preferably, heat sinks do not make up a significant portion of the robotweight.

In a robot intended for effective and efficient use with depot-levelmaintenance and flexible logistics, high-stress, sensitive, andfrequently replaced, refurbished, or rebuilt parts should be readilyaccessible. This can directly compete with an equally important emphasison interchangeable or modularly interchangeable parts.

In a robot intended for flexible use in harsh environments, as manycables, lines, wires, etc. as possible should be internal to thecasing(s) of the robot. Housings and the like should be environmentallyor hermetically sealed, either simply waterproof or made more immersible(e.g., under positive internal pressure). Sufficient sealing ofhousings, cablings, transmissions, and the like can permit a robot to besubmersible.

Further, interference or occlusion among moving parts, static parts, andsensor fields of view preferably do not prevent the robot fromaccomplishing any mission for which it was designed. More particularly,a main chassis, shifting body or load for shifting CG, and drive trackshave a certain volume within which they operate, and as little volume aspossible (outside these bodies) should be filled with motive driveelements.

FIG. 29 provides a partially exploded view of an implementation of alarge skid-steered robot 1000 having a shiftable CG load 510 connectedto the chassis 20 by a sealed linkage 70 driven at chassis end 70A anddriven at the distal (load) end 70B. The shiftable load 510, including abattery box 92 and tilt motor 73, can move rearward to occupy a freespace 21 shown in the middle of the chassis 20 (“Chassis free space”).

FIGS. 30-31 show, respectively, schematic side and top views of animplementation of a large skid-steered robot 1000A having a chassis 20supported on right and left drive track assemblies, 30 and 40respectively, having driven tracks, 34 and 44 respectively. Each driventrack 34, 44, is trained about a corresponding front wheel, 32 and 42respectively, which rotates about front wheel axis 15. Right and leftflippers 50 and 60 are disposed on corresponding sides of the chassis 20and are operable to pivot about the front wheel axis 15 of the chassis20. Each flipper 50, 60 has a driven track, 54 and 64 respectively,about its perimeter that is trained about a corresponding rear wheel, 52and 62 respectively, which rotates about the front wheel axis 15. Ashiftable center of gravity (CG) load 510 is connected to the chassis 20by a sealed linkage 70 driven at a chassis end 70A and driven at adistal (load) end 70B. The shiftable load 510 can tilt (via a tilt motor73 in the load in this implementation, but other implementations mayemploy a chassis-mounted motor) and can move rearward to occupy a freespace 21 in the middle of the chassis 20 (“Chassis free space”) rear ofthe drive wheels 32, 42, structurally surrounded by some chassiselements, and can shift (e.g., swing) or otherwise move forward throughfree space 21 forward of the chassis 20 and forward of the drive wheels32, 42. Motive power elements that generate potentially problematicexcess heat (e.g., motors 36, 46, 72, 74, motor drivers and amplifiers,and batteries 92) are located within the tracks 30, 40 of the maindrive, within the chassis 20 adjacent the main drive wheels 32, 42, andwithin the shiftable CG load 510. As shown in FIG. 31, the location Swithin the shiftable load 510 of motive power element A1 is shiftablefront to rear to move the center of gravity of the entire robot 1000A.This configuration does not include a motive power element in the frontflipper volume.

FIGS. 32-33 show, respectively, schematic side and top views of animplementation of a large skid-steered robot 1000B having a chassis 20supported on right and left drive track assemblies, 30 and 40respectively, having driven tracks, 34 and 44 respectively. Each driventrack 34, 44, is trained about a corresponding front wheel, 32 and 42respectively, which rotates about front wheel axis 15. Right and leftflippers 50 and 60 are disposed on corresponding sides of the chassis 20and are operable to pivot about the front wheel axis 15 of the chassis20. Each flipper 50, 60 has a driven track, 54 and 64 respectively,about its perimeter that is trained about a corresponding rear wheel, 52and 62 respectively, which rotates about the front wheel axis 15. Ashiftable center of gravity (CG) load 510 is connected to the chassis 20by a sealed linkage 70 driven at a chassis end 70A and driven at adistal (load) end 70B. The shiftable load 510 can tilt and can moverearward to occupy a free space 21 in the middle of the chassis 20(“Chassis free space”) rear of the drive wheels 32, 42, structurallysurrounded by some chassis elements, and can swing or otherwise moveforward through free space 21 forward of the chassis 20 and forward ofthe drive wheels 32, 42. Motive power elements that generate potentiallyproblematic excess heat (e.g., motors 36, 46, 72, 74, motor drivers andamplifiers, and batteries 92) are located within the tracks 30, 40, 50,60 of the main drive, within the chassis 20 adjacent the main drivewheels 32, 42, in the front flipper volume, and within the shiftable CGload 510. As shown in FIG. 33, the location S within the shiftable loadof motive power element A1 is shiftable front to rear to move the centerof gravity of the entire robot 1000B; and the location F within theshiftable front flippers 50, 60 is shiftable front to rear to move thecenter of gravity of the entire robot 1000B. The depicted arrows showthese shiftable loads at both ends of their movement range.

FIGS. 34-35 show, respectively, schematic side and top views of anembodiment of a large skid-steered robot 1000C having a chassis 20supported on right and left drive track assemblies, 30 and 40respectively, having driven tracks, 34 and 44 respectively. Each driventrack 34, 44, is trained about a corresponding front wheel, 32 and 42respectively, which rotates about front wheel axis 15. A shiftablecenter of gravity (CG) load 510 is connected to the chassis 20 by asealed linkage 70 driven at a chassis end 70A and driven at a distal(load) end 70B. The shiftable load 510 can tilt and can move rearward tooccupy a free space 21 in the middle of the chassis 20 (“Chassis freespace”) rear of the drive wheels 32, 42, and structurally surrounded bysome chassis elements. The shiftable load 510 can also swing orotherwise move forward through free space 21 forward of the chassis 20and forward of the drive wheels 32, 42. Motive power elements thatgenerate potentially problematic excess heat (e.g., motors 36, 46, 72,74, motor drivers and amplifiers, and batteries 92) are located withinthe tracks 30, 40 of the main drive, within the chassis 20 adjacent themain drive wheels 32, 34, and within the shiftable CG load 510. As shownin FIG. 35, the location S within the shiftable load of motive powerelement A1 is shiftable front to rear to move the center of gravity ofthe entire robot 1000C. This configuration does not include flippers 50,60 as FIGS. 30-33, but may include other kinds of tracks or wheelsconfigured to overcome forward or rearward obstacles.

A feature of the robotic vehicle 10, 1000, 1000A, 1000B, 1000C is theplacement of a motive power element A4 as shown in FIGS. 30-35 (battery,motor, motor driver amplifier). This element typically generatessignificant waste heat (e.g., at least 5% losses to heat), produced byparts such as motor drivers and amplifiers, at least partially withinthe volume D (in “A4-D”) of the main tracks, and also either directlynext to the main chassis 20 or substantially next to the main chassis 20(for example, via similarly cast and/or machined intervening plate(s) 26flush-mounted for thermal conduction to the main chassis 20). In someimplementations, each of the chassis 20 or intervening plates 26 is mademostly of materials recognized to be structurally robust, light, anduseful heat sinks when sufficient surface area and/or volume isavailable (e.g., thermal conductivities of greater than 50 W/(m·K), andpreferably greater than 100 W/(m·K) such as aluminum at 237 W/(m·K) at300 K, magnesium at 156 W/(m·K) at 300 K, and alloys).

In this location, the heat generated (e.g., at least about 5% losses on500 W peak, but also up to the same losses or higher on 2 kW peak orhigher) is dissipated via the 50-100 lb. chassis. In preferredimplementations, the motive power element A4 is readily accessible fromthe side of the robot 10,1000, and may be serviced readily, anyassemblies placed therein being slide-able or translatable in ahorizontal direction for removal from the track or drive volume orenvelope D. The motive power element A4 is located at least partlywithin the track/wheel volume D, yet does not impede movement of thetracks 30, 40 or wheels 32, 42; and is located at least partly withinthe chassis 20, yet does not impede movement of mechanism or load forshifting the center of gravity (e.g., Shift CG load). Very little volumeis occupied beyond the volume already necessary for the chassis 20 andtracks/wheels 30, 40, 32, 42 themselves. The motive power element A4 canbe sealed against the environment and immersion-proofed (e.g., via acover 27 and plate 26), as any wiring from the motive power element A4to another motive power element adjacent the wheels (e.g., A2) is routedwithin the chassis 20, without necessarily passing through anyslip-rings or other moving conductive junctions. Wiring to anothermotive power element (e.g., A1) via the chassis for shifting the centerof gravity is routed within the sealed (e.g., welded, cast, sealed)linkage 70 between chassis 20 and CG-shifting load 510. Because the maintrack/wheel volume or envelope D is generally symmetrical (left andright sides of the vehicle being mirror-able), the motive power elementA4 to be placed within that envelope D may be the same size and shape oneach side, which permits an additional functionality in thatinterchangeable and/or modular assemblies to be used for the motivepower element A4 in those two locations.

If the motive power element A4 is a motor driver/amplifier for drivemotors 36, 46 adjacent the wheels 32, 52, 42, 62, in the chassis 20, orif the motive power element A4 is a drive motor 36, 46 driven by a motordriver/amplifier adjacent the wheels 32, 52, 42, 62 within the chassis20 (e.g., at A2), the distance to the drive motors 36, 46 can be short,e.g., between a drive wheel radius distance and a distance to a rearwheel (i.e., within the skid steer wheel or track envelope D), resultingin drive cabling or wiring that generates minimal EM emissions. Theplacement of these motor drivers and amplifiers A4 at this location D,in combination with drive motors 36, 46 placed adjacent drive wheels 32,52, 42, 62 but within the chassis 20 (e.g., within location C of“A2-C”), contributes to the advantages of a preferred combination ofmorphology and placement of motive power elements of the robot 10, 1000.

Another feature of the robotic vehicle 10, 1000 is the placement of amotive power element A2 generating significant waste heat adjacent adrive wheel 36, 46 (in position “C” of “A2-C”), and also either directlynext to the main chassis 20 or substantially next to the main chassis 20(via similarly cast and/or machined intervening plate(s) flush-mountedfor thermal conduction to the main chassis 20), each of the chassis 20or intervening plates 26 made in cast or machined form mostly of thestructural, heat conductive materials discussed above.

In this location, the heat generated (e.g., at least about 5% losses onabout 500 W peak, but in this location more likely to be motive powerelements A2 of the main drive, having at least these losses on about 2kW peak or higher) is dissipated via the chassis 20. The motive powerelement A2 is serviced by, e.g., removing the main tracks 30, 40. Inpreferred implementations, the motive power element A2 is located withinthe chassis 20, so does not impede movement of mechanism or load 510 forshifting the center of gravity (e.g., Shift CG load). Little additionalvolume is occupied beyond the volume already necessary for the chassis20 itself. The motive power element A2 can be sealed against theenvironment and immersion-proofed, as any wiring from the motive powerelement A2 to another motive power element (e.g., A4) within the trackor drive envelope or volume D is routed within the chassis 20, withoutnecessarily passing through any slip-rings or other moving conductivejunctions. Because the chassis volume or envelope C is generallysymmetrical (left and right sides of the vehicle being mirror-able), themotive power element A2 to be placed within that envelope C may be thesame size and shape on each side, which permits interchangeable and/ormodular assemblies to be used for the motive power element in those twolocations C.

If the motive power element A2 is a drive motor 36, 46 or other motor, asecond motor (motive power element) may be located above or partiallyconcentric with the drive motor 36, 46 or other motor; and acorresponding/driving motor driver/amplifier may be located at leastpartially within the envelope or volume of main tracks D. With a poweredskid steered or differential drive as a base platform, two drive motors36, 46 for the two sides of the platform 20 may be as close as possibleto a driven wheel 32, 42 (contacting the ground or inside of a track),with compact transmissions (e.g., a planetary gear train). Transmissionsextending over longer distances (shafts, chains) are possible, but notpreferable (e.g., these would tend occupy space that would be morepreferably available for payload, movement of manipulators, or sensorfields of the robot).

Another feature of the robotic vehicle 10, 1000 is the placement of amotive power element A1 (or A3) generating significant waste heat aspart of, and within, a load 80, 90, 510 shifted for the purpose ofmoving the center of gravity of the vehicle 10, 1000, for example. Ifthis motive power element A1 is heavy (e.g., 25%-50% or more of theentire vehicle 10, 1000 in combination with the rest of a load shiftedto move the CG), the center of gravity of the entire vehicle is movedmore. Two possible locations for the motive power element A1contributing to shifting the center of gravity are in position S (of“A1-S”) within a main load 510 shifted by a linkage 70, or distributedbetween and/or within the volume F (of “A3-F”) of front flippers 50, 60rotatable with respect to main drive skid steering tracks 30, 40 orwheels 32, 42. In either case, the motive power element A1 (and/or orA3) should be directly next to and/or flush-mounted for thermalconduction to a sub-chassis (e.g., the battery box 90 together with mainelectronics/CG tub 90), which is made of the cast and/or machinedstructural, heat conductive materials discussed above.

In these locations S (or F), the heat generated (e.g., at least about 5%losses on about 500 W peak, but in these locations also likely to beinclude higher losses on a battery pack serving 42V, 30 A continuouspower) is dissipated via the sub-chassis. A motive power element A1 inthe linkage-shifted load 510 is readily serviced by opening the top deck80; and a motive power element A3 distributed between the front flippervolumes F is readily accessible and serviced with similar advantages tothe earlier discussed motive power element partially within the maindrive volume D. The motive power element A1 in the linkage-shifted load510 does not impede movement of the linkage 70 or main drive 36, 46, 30,40, and a motive power element A3 within the flipper volume F similarlydoes not impede movement of linkage 70 or main drive 36, 46, 30, 40. Forthe front flippers 50, 60, very little volume is occupied beyond thevolume already necessary for the flipper tracks 54, 64 themselves. Amotive power element A1 in the linkage-shifted load 510 can be sealedagainst the environment and immersion-proofed, as any wiring from thismotive power element A1 to another motive power element within thechassis 20 or drive envelope or volume D is routed within the sealedlinkage 70. A motive power element A3 (or alternatively, other elementsuch as reserve batteries or storage box) within the front flippervolume F can also be readily sealed. Because the front flipper volumes Fare generally symmetrical (left and right sides of the vehicle beingmirror-able), an element to be placed within that envelope may be thesame size and shape on each side, which permits interchangeable and/ormodular assemblies to be used for the element in those two locations.

If the motive power element A1 in the linkage-shifted load 510 is abattery assembly 92, power may be transferred via the linkage 70, andmotor driving signals need not be, leading to lower EM emissions and an“EM quiet” configuration.

Another feature of the robotic vehicle 10, 1000 is the provision of two,for example a 500 W and 2 kW peak, motor driver/amplifiers within thesame enclosure, at least partially within the volume of the main tracksD, and also either directly next to the main chassis 20 or substantiallynext to the main chassis, either of the chassis 20 or intervening plates26 made mostly of the structural, heat conductive materials discussedherein.

In some implementations, the robot 10, 1000 has two main drive motors36, 46 and three auxiliary motors (one flipper actuator 55, two linkagepivot motors 72, 74 that shifts a load 510 and/or payload in order toshift the CG of the vehicle 10, 1000). At least the flipper motor 55 islocated in the forward chassis 20 adjacent the main drive 36, 40 (e.g.,a location C of “A2-C”), the flippers 50, 60 being rotatedconcentrically about the front skid steer drive wheel axis 15. Inaddition, a motor 72 for shifting the load 510 (and CG) is alsoadvantageously located in the forward chassis 20 adjacent the main drive36, 40 (e.g., a location C of “A2-C”). If the motor 55 for rotating theflippers 50, 60 (or other mobility element) is substantially similar tothe motor 72 for rotating the CG-shifting load, these may be driven bythe same motor driver/amplifier. In a location at least partially withinthe volume D of the main tracks 30, 40 and optionally partly within thechassis 20, the heat generated (e.g., by a combination of two motordriver/amplifiers: one for the main drive motor 36, 46 having at leastabout 5% losses to heat on 2 kW peak or higher, as well as the smaller500 W flipper or shifter motor) by two different motordrivers/amplifiers (two on each side of the robot) is dissipated via thechassis 20. These motive power elements A4 (four different motordriver/amplifiers) are readily accessible from the side of the robot 10,1000, and may be serviced readily, slideable or translatable in ahorizontal direction. These motive power elements A4 are located atleast partly within the track/wheel volume D, do not impede movement ofmechanism or load 510 for shifting the center of gravity, and littlevolume is occupied beyond the volume already necessary for the chassis20 and tracks/wheels 30, 40, 32, 42. These motive power elements A4 canbe sealed together against the environment and immersion-proofed, as anywiring from one of the motive power elements A4 to another motive powerelement adjacent the wheels 32, 42 (e.g., A2-C) is routed within thechassis 20, without necessarily passing through any slip-rings or othermoving conductive junctions. Wiring to the four motors 36, 46, 55, 72 inthe chassis 20 for drive, flippers, and shifting the center of gravityis routed within chassis 20. These motive power elements A4 may be thesame size and shape, so that interchangeable and/or modular assembliesto be used for the motive power elements in those two locations can beused, even though one side drives one main drive and flipper, while theother side drives one main and CG shifter.

Again, for these motor driver/amplifiers in locations D of “A4-D”, thedistance to the drive motors 36, 46 can be short, e.g., between a drivewheel radius distance and a distance to a rear wheel (i.e., within theskid steer wheel or track envelope), resulting in drive cabling orwiring that generates minimal EM emissions—from four separate motors.The placement of these four different motor drivers 36, 46, 55, 72 andamplifiers at these locations D of “A4-D”, in combination with drive,flipper, and shifter motors A2 placed adjacent drive wheels but withinthe chassis (e.g., at locations C of “A2-C”), contributes to theadvantages of a preferred combination of morphology and placement ofmotive power elements of the robot 10, 1000.

As shown in FIGS. 7 and 29, this configuration of motive power elementswithin the chassis, track volume C, D, and shiftable load 510 may resultin a fully environmentally sealed robot needing no exposed wiring, yethaving many replaceable parts readily serviceable and modular. Thechassis 20 is cast then machined, and includes cavities C into which aremounted four motors 36, 46, 55, 72 and transmissions. These cavities Care sealed by a plate-transmission arrangement that leaves exposed onlya sealed drive main spline (seen in FIG. 29). Internally, the cavities Care connected to mounts for the linkage 70 and to further side cavitiesD. Wiring is internally routed from the motors 36, 46, 55, 72 in C tothe motor drivers and amplifiers within cavities D. These cavities D areenvironmentally sealed with a plate 26 and cover 27, serviceable throughthe main tracks 30, 40. Wiring is also internally routed from thechassis 20 general and cavities C through the mounts for the linkage70—one left-right lateral side of the linkage 70 is used for a swingactuator 72 at the bottom 70A and tilt actuator 74 at the top 70B, andthe remaining left-right-side routes cables. The linkage 70 is sealed atthe bottom 70A and the top 70B. The tilt actuator 74 at the top 70B isanother motive power element that generates heat. However, the batteryassembly 92 in the shiftable CG load 510, 80 generates more heat that issunk into the machined casting of the battery box 92, deck 80, andelectronics tub 90.

FIG. 36 provides a schematic view of the controller, drive and actuatorsystem of a preferred control system for robotic vehicle 10. The roboticvehicle 10 includes a main computer 5320 which runs control logic 5400to control the robotic vehicle 10. The main computer 5320 communicateswith the drive modules 5500 and the actuator modules 5600 over a motorcontrol controller area network (CAN) bus 5325.

FIGS. 36 and 37A-D depict a track drive module 5500. The track drivemodule 5500 includes a module housing 5502, a motor 5530 supported bythe module housing 5502, and a motor controller 5510 supported by themodule housing 5502 and in communication with the motor 5530. In oneinstance, the motor 5530 is a low inductance-high power 2000 W motorproviding between about 2000-10500 maximum revolutions per minute. Thisis only an example and the motor design may vary based on requiredcapabilities and other design constraints. In one implementation, thetrack drive module 5500 further includes a back-drivable gearbox 540(e.g. a planetary gearbox) supported by the module housing 5502 andcoupled to the motor 5530. In one example, the gearbox 5540 provides a30:1 gear reduction. In the depicted implementation, the drive module5500 is also sealed within a respective receptacle, 22, 24, of thechassis 20 from an outside environment and is passively cooled.

FIGS. 36 and 38A-B depict an actuator module 5600. The actuator module5600 includes a module housing 5602, a motor 5630 supported by themodule housing 5602, and a motor controller 5610 supported by the modulehousing 5602 and in communication with the motor 5630. In one instance,the motor 5630 is a low inductance-high power 500 W motor providingbetween about 17K-20K maximum revolutions per minute. In oneimplementation, the actuator module 5600 further includes aback-drivable planetary gearbox 5640 supported by the module housing5602 and coupled to the motor 5530. In one example, the gearbox 5540provides a 1700:1 gear reduction. The actuator module 5600 also includesa slip clutch 5650 supported by the module housing 5602 and coupled tothe planetary gearbox 5640. The slip clutch 5650 absorbs impacts to theactuator module 5600. For example, when the robotic vehicle 10 maneuversdown off of a ledge onto a ground surface the flippers 50 and 60 incuran initial landing impact that creates a large moment about the frontwheel axis 15. The slip clutch 5650 allows the flippers 50 and 60 torotate while overcoming a frictional resistance of the slip clutch 5650,thereby absorbing the impact and avoiding damage to the gearbox 5640.Likewise, a sudden impact to the payload deck 80 is absorbed by the slipclutch 5650 in the actuator modules 5600 located at the first and secondpivots, 71 and 73 respectively. For example, a disruptor module attachedto the payload deck 80 will experience recoil when detonating bombs. Theslip clutch 5650 in the actuator modules 600 located at the first andsecond pivots, 71 and 73 respectively, will absorb the sudden recoil,thereby avoiding damage to the gearbox 5640. An absolute positionencoder 5660 disposed on an actuator shaft 5606 provides an absoluteposition of the actuator shaft 5606 to the actuator controller 5610.

Each module, 5500 and 5600, includes a power connector, 5504 and 5604respectively, disposed on an outer surface of the module housing, 5502and 5602 respectively. The power connector, 5504 and 5604, is configuredto mate with a corresponding power bus connector 5326 to establish anelectric power connection to the module, 5500 and 5600 respectively. Thedrive module 5500 establishes an electric power connection with the buspower connector 5326 within its respective receptacle 22, 24 as themodule 5500 is placed within the receptacle 22, 24.

In another aspect, a robotic vehicle 10 includes a chassis 20 havingfront and rear ends, an electric power source 90 (e.g. a bank of ninestandard military BB-2590 replaceable and rechargeable lithium-ionbatteries or a fuel cell) supported by the chassis 20, and multipledrive assemblies, 30 and 40, supporting the chassis 20. Each driveassembly, 30 and 40, includes a track, 34 and 44, trained about acorresponding drive wheel, 32 and 42, and a drive control module, 36 and46. Each drive control module, 36 and 46 (also referred to as 5500),includes a drive control housing 5502, a drive motor 5530 carried by thedrive control housing 5502 and operable to drive the track, 34 and 44respectively, and a drive motor controller 5510 in communication withthe drive motor 5530. The motor controller 5510 includes a signalprocessor 5515 (preferably a digital signal processor (DSP)) and anamplifier commutator 5520 in communication with the drive motor 5530 andthe signal processor 5515 and capable of delivering both amplified andreduced power to the drive motor 5530 from the power source 90. Theability to provide both amplified and reduced power to a lowinductance-high power drive motor 5530 provides a dynamic drive rangewith a gear reduction box 5540, rather than a complex transmission.

In one implementation, the track drive module 5500 includes a DC drivemotor 5530, where regenerative braking can be obtained on applicationsrequiring quick stops. DC motor-generated energy is fed back into theelectric power source 90 of the dc motor, replenishing available power.In one example, the signal processor 5515 uses a resistive load toprevent regenerate energy from passing back to the pour source 90.

In another implementation, the actuator module 5600 includes a DC drivemotor 5630, where regenerative braking can be obtained on applicationsrequiring quick stops or when experiencing recoils such as when the slipclutch 5650 absorbs an impact or recoil. DC motor-generated energy isfed back into the electric power source 90 of the dc motor, replenishingavailable power. In one example, the signal processor 5615 uses aresistive load to prevent regenerate energy from passing back to thepour source 90. Furthermore, a magnetic brake within the motor 5630inhibits actuation upon power loss.

FIG. 39A is a block diagram of the drive control module 5500. Theamplifier commutator 5520 includes a commutator 5526 in communicationwith the drive motor 5530, a DC/DC converter 5524 capable of deliveringboth amplified (boost) and reduced (buck) power to the commutator 5526,and a programmable logic circuit (e.g. a complex programmable logicdevice (CPLD)) 5522 in communication with the signal processor 5515,DC/DC converter 5524, and commutator 5526. The amplifier commutator 5520allows for control of high torque, brushless or brushed motors withfairly accurate position control. In one implementation, the amplifiercommutator 5520 includes two stages. The first stage provides largemotor torque and includes a DC/DC converter 5524 for providing voltageto the second stage. The second stage includes a three-phase bridgecommutator 5326 that allows for control of different kinds of motors.The power supply to the commutator 5326 is controlled by a combinationof voltage control from the DC/DC converter 5524 via pulse-widthmodulation (PWM) control to the programmable logic circuit 5522 andcurrent control via the FETS/commutators of the commutator 5526.

In some examples, the motor controller 5510 communicates with a motorsystem 5531 which includes the motor 5530, multiple magnetic fieldsensors 5532 (e.g. Hall effect sensors) mounted radially about the motor5530 to detect magnetic pulses, a velocity sensor 5534 (e.g. anencoder), and a rotary position sensor 536 (e.g. an analog positionsensor). The magnetic field sensors sensor 5532 measures a motor rotorposition or other position information associated with the motor 5530and provides a feedback signal to the programmable logic circuit 5522.The signal processor 5515 also receives feedback with respect to themotor 5530 from the velocity sensor 5534 and the rotary position sensor5536. The position sensor 5536 obtains position data associated with thegearbox 5540 or the shaft 5506. Based on these feedback signals, thesignal processor 5515 can change the duty cycle of the PWM signals. Inone example, the motor system 5531 also includes a temperature sensor5538 that measures a motor temperature and provides a feedback signal tothe signal processor 5515.

FIG. 39B depicts one example of the DC/DC converter 5524. The circuitryfor providing buck and boost includes two switches, two diodes, atransistor, and a current storage element including an inductor and acapacitor. The order of these components dictates whether the DC/DCconverter 5524 provides buck or boost. A bank of FETs switch thedirection of current flow in the circuit and therefore its operation. Inone example, the DC/DC converter 5524 receives about 42 V from the powersource 90 and is capable of delivering between about 0 V and about 150V. The power source 90 may include three 14 V batteries in series andthree 14 V batteries in parallel, providing 42 V to the robotic vehicle10. Furthermore, a current from the power source 90 is controlled by aninrush current limiter 95.

The signal processor 5515 controls the amplifier commutator 5520. Whenthe robot controller 5320 (e.g. a single board computer) sends a drivecommand to a drive module 5500, the signal processor 5515 determineswhether power amplification (boost) or reduction (buck) is required toperform the command. The signal processor 5515 communicates with theprogrammable logic circuit 5522 to operate the DC/DC converter 5524accordingly to provide the appropriate power to the commutator 5526,which drives the motor 5530.

The motor controller 5510 can supply drive signals to a motor 5530, suchas a brush motor, 3-phase induction motor in scalar control mode orvector control mode (using an encoder), or brushless DC motor insinusoidal or PWM (using an encoder), and a three-phase AC motor. Halleffect sensors 5532, quadrature encoding 5534, and a position sensor5536 are available for speed/position feedback (in addition to feedbackfrom the commutators, etc.).

Both the signal processor 5515 and the programmable logic circuit 5522can conceivably be considered part of each stage, because of their(control) contribution to e.g., DC/DC conversion in stage 1 (setting thevoltage) and to running the FETS of the commutator 5326 in stage 2. TheDC/DC converter 5524 increases/decreases and regulates an input powerand can be connected to an inductor. The DC/DC converter 5524 receives apulse-width modulation (PWM) signal from the signal processor 5515 viathe programmable logic circuit 5522 having a duty cycle proportional tothe required power. For example, the PWM signal can control one or moreswitches in the DC/DC converter 5524 which control the voltage orcurrent out of the DC/DC converter 5524. The signal processor 5515 sendstwo PWM signals to the programmable logic circuit 5522 with a duty cycleproportional to current command. PWM1 controls a high site MOSFET andPWM2 controls a low site MOSFET. To avoid through shot current, PWM1 andPWM2 signals have dead time between falling and rising edges. The deadtime can be set by signal processor 5515, and it can be, for example,125 nSec. In one implementation, the PWM frequency is 30 kHz. FIGS.39B-C each provide schematic diagrams of example DC/DC converters 5524.Standard electrical symbols known in the art of electronics should beused in interpreting the schematics.

The programmable logic circuit 5522, in one example, providescommutation signals for six power MOSFETs of the commutator 5326assembled as a three phase bridge and acts as a protection device for avariety of signals. FIG. 39D provides a schematic diagram of one exampleof a commutator 5326. The commutation signals provided by theprogrammable logic circuit 5522 result from a logic conversion of inputsfrom three Hall effect sensors 5532 and a direction input from thesignal processor 5515. Six output signals from the programmable logiccircuit 5522 are received by and control the power MOSFETs of thecommutator 5326. Commutation signals can be generated for 60° or 120°spaced Hall sensors 5532. Protection logic verifies that Gray Code isnot violated. In cases where a violation of Gray Code or Hall conditionsoccur, a commutation fault signal is established. The commutationsequence changes depending on the direction command.

The signal processor 5515 may send a signal to the programmable logiccircuit 5522 to operate in a brushless mode or a brush mode.Accordingly, commutation signals can be generated for brushed andbrushless DC motors. In brushless mode, the programmable logic circuit5522 receives a feedback signal from the Hall effect sensors 5532 andsends control signals based on the Hall sensor feedback signal to anH-bridge included with the commutator 5326 to control the motor 5530.The signal processor 5515 uses commutation signals from tablesassociated with brushless operation and sends a signal to the commutator5326 accordingly. In brush mode, the signal processor 5515 receivesfeedback from the encoder 5534 and sends control signals to thecommutator 5326 through the programmable logic circuit 5522 based atleast in part on an encoder signal. The programmable logic circuit 5522uses commutation signals from tables associated with brush operation andsends a signal to the commutator 5326 accordingly. The commutator 5326controls the motor 5530 using the H-bridge. Furthermore, in the case ofa brushed motor, phase A or B is used to commutate the motor dependingon the direction command.

After receiving the operation mode, the programmable logic circuit 5522provides a control signal to the commutator 5326. The commutator 5326drives the motor 5530 with DC power from the DC/DC converter 5524 andchanges a direction of motor rotation based on direction control signalsfrom the signal processor 5515 via the programmable logic circuit 5522.The signal processor 5515 can receive a current sensing feedback signalfrom the commutator 5326 and use the current sensing feedback signal tocontrol a duty cycle of the PWM signals to the DC/DC converter 5524.

The signal processor 5515 includes three cascading control loops for: 1)motor current (≈a torque) and commutation; 2) motor voltage (≈a speed);and 3) motor rotor position. The signal processor 5515 monitors feedbackfrom the motor current at about 30 kHz (33 μSec), the motor voltage atabout 250 Hz (4 milliseconds), and the motor rotor position at about 50Hz (10 milliseconds). For each current control loop iteration, thesignal processor 5515 reads the current sensing feedback from thecommutator 5326, reads the Hall effect sensors 5532, computes a PWMoutput, writes the PWM output to a shared structure accessible by theother control loops, and updates a cycle counter. The signal processor5515 monitors the Hall effect sensors 5532 to insure that they do notall have the same value. For each voltage control loop iteration,triggered by a software interrupt in the current control loop, thesignal processor 5515 reads a velocity feedback from the encoder 5534,reads the voltage feedback from the DC/DC converter 1524, and computes acommanded current based on a current limit, maximum current from athermal protection model, and a current rate of change limit. The signalprocessor 5515 writes the commanded current to a shared structureaccessible by the other control loops. The signal processor 5515 alsochecks for a stall condition and for regenerative braking. Ifregenerative braking is detected, the signal processor 5515 checks theavailable power level of the power source 90 and charges the powersource 90 until a charged level is attained. For each position controlloop iteration, the signal processor 5515 reads the position feedbackfrom the position sensor 5536, computes a commanded velocity based oncurrent and velocity limits, and writes the commanded velocity to ashared structure accessible by the other control loops.

Referring to FIGS. 39E-G, for the drive module 5500 and the actuatormodule 5600, the motor control logic on the DSP 5515, 5615 provides abuck-PWM, which is PWM control from 0 volts to a supply voltage; abrake-PWM, which is PWM control of a dummy load resister across themotor 5530, 5630; a direction bit, which sets the commutation directionfor the CPLD 5522; and a commutation inhibit, which inhibits commutationwhen the motor 5530, 5630 is acting like a generator. For the drivemodule 5500, the motor control logic on the DSP 5515 also provides aboost-PWM, which is PWM control of a voltage booster for the motor 5530to command more than the supply voltage to the motor 5530.

In a positioning system, a motor current loop (controlling acceleration)forms a part of a velocity loop (controlling motor speed), which in turnis part of an outer loop of position, which has desired position as areference. An error in position calls for more or less speed, and anerror in speed calls for more or less acceleration (current). Each loopmust be stabilized, or preferably optimized, starting with the innermostloop.

The control structure includes a torque (or current) PID(Proportional-Integral-Derivative) control loop 51000 and a velocity PIDcontrol loop 52000 on top of the current control loop 51000. Eachelement of the PID control loop 51000, 52000 refers to a particularaction taken on an error. An output control variable (CV) is based onthe error (e) between a user-defined set point (SP) and a measuredprocess variable (PV). The proportional element is the error multipliedby a gain, Kp. This is an adjustable amplifier and is responsible forprocess stability (e.g. too low and the PV can drift away; too high andthe PV can oscillate). The integral element is an integral of errormultiplied by a gain, Ki, which is responsible for driving the error tozero. However, setting Ki too high invites oscillation or instability,integrator windup, or actuator saturation. The derivative element is arate of change of error multiplied by a gain, Kd, which is responsiblefor system response (e.g. too high and the PV will oscillate; too lowand the PV will respond sluggishly). Tuning of a PID involves theadjustment of Kp, Ki, and Kd to achieve some user-defined “optimal”character of system response. Another adjustment for achieving anoptimum performance may include maximizing low frequency gain, Kf, andminimizing high frequency gain, Kf.

The torque (current) control loop 51000 includes a voltage loop 51100and a dummy load or brake loop 51200. The torque control loop 51000 alsodetermines a direction bit 51300 of the commutator 5526. The inputcommand current is rate and value limited. A sign (+/−) of the limitedcommand current is used to determine a desired motor direction.

Referring to FIG. 39F, a motor current direction state diagram, thereare four motor current direction states, which include a MOTOR_FWD state51502, a MOTOR_FWD_TO_REV state 51504, a MOTOR_REV state 51506, and aMOTOR_REV_TO_FWD state 51508. The MOTOR_FWD state 51502 exists when themotor 5530 is running in a forward direction. The MOTOR_REV state 51506exists when the motor 5530 is running in a reverse direction. TheMOTOR_FWD_TO_REV state 51504 is a transitional state when the motor 5530is changing from the forward direction to the reverse direction. TheMOTOR_REV_TO_FWD state 51508 is also a transitional state when the motor5530 is changing from the reverse direction to the forward direction. Ifthe motor current direction state is MOTOR_FWD 51502, then if thelimited command current is less than zero, move to the MOTOR_FWD_TO_REVstate 51504. If the current direction state is MOTOR_REV, then if thelimited command current is greater than zero, move to theMOTOR_REV_TO_FWD state 51508. If the current direction state isMOTOR_FWD_TO_REV 51504, then if an absolute value of the motor speed isless than a change direction speed, move to the MOTOR_REV state 51506.If the limited command current is greater than zero, move to theMOTOR_FWD state 51502. If the current direction state isMOTOR_REV_TO_FWD 51508, then if an absolute value of the motor speed isless then the change direction speed, move to the MOTOR_FWD state 51502.If the limited command current is less than zero, move back to theMOTOR_REV state 51506. The change direction speed is the fastest speedthe motor can operate at while changing the commutation direction bychanging the direction bit 51300. Changing the direction bit 51300 whileoperating the motor 5530 at a faster speed could destroy the FETs 5526controlling the motor 5530. The state machine described above is set upto change the direction bit 51300 in a controlled manner, therebyavoiding damage to the system. The direction bit 51300 is set once acurrent direction state is determined and the direction bit 51300 ischanged only while in the MOTOR_FWD 51502 or MOTOR_REV 51506 currentdirection states. The direction bit 51300 remains uncharged while intransition current direction states (MOTOR_FWD_TO_REV 51504 orMOTOR_REV_TO_FWD 51508).

Referring to FIGS. 39E and 39G, the mode select block 51050 of motorcontrol logic on the DSP 5515 determines which PID loop (the voltagecontrol loop 51100 or the dummy load control loop 51200) to run. Themotor control logic does not switch between using the voltage controlloop 51100 to control the current and the dummy load control loop 51200to control the current unless the command current changes sign (+/−). Ifthe current direction state is MOTOR_FWD 51502 or MOTOR_REV 51506, themotor control logic runs the voltage loop 51100 in a CTRL_VOLT mode51102 and uses the voltage PWM to control the motor current. If thecurrent direction state is MOTOR_FWD_TO_REV 51504 or MOTOR_REV_TO_FWD51508 and the motor control logic is in a CTRL_VOLT mode 51102 (usingthe voltage to control the current), then if an absolute value of themotor speed is less than the change direction speed, continue in theCTRL_VOLT mode and use the voltage PWM; otherwise, set the motor controllogic mode to CTRL_DUMMY_LOAD 1202 and use the PWM from the dummy loador brake control loop 51200 to slow the motor down. If the currentdirection state is MOTOR_FWD_TO_REV 51504 or MOTOR_REV_TO_FWD 51508 andthe motor control logic is in the CTRL_DUMMY_LOAD mode 51102, continuein the CTRL_DUMMY_LOAD mode 51202 and use the dummy load PWM. If thecurrent is greater than zero, set the motor control logic mode toCTRL_VOLT 51102; else, set the mode to CTRL_DUMMY_LOAD 51202.

Both the voltage PID loop 51100 and the dummy load PID loop 51200 havethe same Integrator decay, Anti-windup, Integrator limiting and commandrate limiting measures as the velocity loop 52000.

Referring again to FIG. 39E, in the voltage control loop 51100, acomputed back EMF needed to keep the motor 5530 at the current speed isadded to the PID loop command. This floats the PID loop 51100, meaningthe PID does not need to create as big a command and does not need tokeep as large a value in the integrator as it would otherwise. While inbuck mode, the control logic uses the current supply voltage as thedivisor when converting the command voltage to % PWM. While inbuck-boost mode, the control logic uses a boost max voltage as thedivisor when converting the command voltage to % PWM. The PMW command issent through a low pass filter 51110, which in buck mode, dithers thePWM command to provide smooth control at low speeds. Some of the bottomand top PWM is lost due to the rising and falling edge delay added tothe PWM generator. A PWM command of zero to min-PWM, is zero in effect.Running the loop 51100 relatively fast allows low pass filtering the PWMcommand without issue. The low pass filter 51110 makes the PWM commandturn on and off proportionally to the lower PWM command, providingvoltage control. In effect, the control logic pulse width modulates thePWM command. In Buck-Boost mode, a dead band exists at an upper end ofthe buck PWM and at a lower end of the boost PWM. The low pass filter51110 of the PWM command dithers the PWM in this range allowing controlof the current even in the dead band.

In the brake or dummy load loop 51200, the control logic computes theestimated resistance needed for the current command (R=Vemf/Icmd) andadds it to the output of the PID loop 51200. Like adding the back EMF inthe voltage loop, this helps float the PID loop 51200 so that it doesnot need as large of gains and integrator wind up. Since the conversionfrom commanded resistance to PWM is non-linear, the control logicconverts a requested resistance to PWM after the PID and estimatedresistance are added together to keep the non-linearity out of the PIDloop 51200. Unlike the voltage loop 51100, a low pass filter is notapplied to the PWM command. Since shoot through is not a concern, thedead band generator is not running, and there is smooth control fromzero to max-PWM.

The current loop 51000 toggles a software watchdog timer at 25 KHz thatis sent to an external watchdog timer, which will reset the DSP 5515 ifthe software stops running. A motor amplifier watchdog to the CPLD 5522is toggled at 25 KHz in the current loop 51000 as long as no hardwarefault is detected, and is used for brown out protection. If the supplyvoltage falls below a brownout voltage, the motor amplifier 5520 isdisabled because the DSP 5515 stops toggling a GPIO bit.

Referring to FIG. 39H, the velocity control loop 52000 is a PID loopthat takes a commanded speed and measured speed as inputs and provides acommanded torque as an output. The velocity control loop 52000 isenhanced by rate limiting the input command and adding an integratoranti-windup, an integrator decay and an integrator limiting measure. Therate of change of the input command to the loop 52000 is limited suchthat a step input is changed to a ramped input, allowing for more gentlecontrol. A maximum speed allowed is also limited. The integratoranti-windup measure stops integration of an error when the control issaturated. Integration is stopped when an issued command is larger thana maximum command allowed by the torque loop 51000 or when the torqueloop 51000 reports that a PWM command has been limited. The integratordecay measure (not shown) allows the integrator to gracefully decay tozero with a zero velocity command. The integrator decay measure isconfigurable from a CAN Object Dictionary (OD). If the input command iszero for more than a set number of control cycles, the integrator decayis set to a value less then one. If the commanded input is non-zero, theintegrator decay measure is set to 1.0. This allows stiff control whilemoving, but relaxes the integrator while not commanding any speed. Inone example, the integrator decay is the value of the current integratorvalue multiplied by each control loop iteration. If the integrator decayis 1.0, the integrator decay stays the same. If the integrator decay is0.99, the value of the integrator slowly fades, unless it is integratinga non-zero error. The integrator limiting measure (not shown) limitsminimum and maximum values sent to the integrator.

Exclusive OR logic in the programmable logic circuit 5522 protectsoutput signals from having high level conditions at the same time forthe high and low site MOSFETs. The programmable logic circuit 5522 may,for example, take configuration data as follows: Motor type: brushed orbrushless; Motor: enable or disable; Hall sensor: 60° or 120°; Faultclear; DC/DC—PWR Over current: enable or disable; and Direction:clockwise or counter-clockwise.

In some implementations, a health monitor 5518 receives data associatedwith the motor 5530 and/or motor controller 5510 components. If thesecomponents are not functioning properly, the health monitor 5518 sends asignal to the programmable logic circuit 5522 to cease sending the PWMsignal to the DC/DC converter 5524 and shuts off power to the motor5530.

FIGS. 40A-B together provide a schematic diagram of one implementationof a drive control module 5500. In some examples, the signal processor515 and/or programmable logic circuit 5522 may be accessed by the robotcontroller 5320 to perform other types of processing besides motorcontrol and amplification. For example, the signal processor 5515,programmable logic circuit 5522, and/or and another processor device,such as a field programmable gate array (FPGA) may be used by the robotcontroller 5320 to perform specialized logic processing associated withrelatively large vector arrays, floating point computations, or otherrequirements, as needed to control the robotic vehicle 10.

In one example, the drive modules 5500 have a maximum operating power ofabout 2000 W and the actuator modules 5600 have a maximum operatingpower of about 500 W. In each module, 5500 and 5600, the signalprocessor, 5515 and 5615, and the amplifier commutator, 5520 and 5620,are mounted on a single plate, which is located in close proximity tothe motor, 5530 and 5630, to minimize noise, reduce cabling, and providea compact module, aiding modularity and interchangeability.

In another aspect, a method of controlling a robotic vehicle 10 includesproviding a robotic vehicle 10 that includes a chassis 20 having frontand rear ends, an electric power source 90 supported by the chassis 20,and a drive assembly, 30 and 40, supporting the chassis 20, and drivenby a drive control module 500 as described above. The method alsoincludes providing a robot controller 5320 with a power managementcontrol logic 5411 that recognizes a power source type and monitors anavailable power level. The robot controller 5320 communicates over acontroller area network (CAN) bus 5325 to the signal processors 5515 ofeach drive control module 500 to deliver drive commands based on thepower source type and the available power level. If the power managementcontrol logic 5410 detects a low power level or high power sourcetemperature, the robot controller 5320 will avoid sending powerintensive commands to the drive control modules 5500 and the actuatormodules 5600.

Referring to FIG. 36, the robot controller 5320 communicates over apower-auxiliary sensors-payload deck CAN bus 5328 to a power andauxiliary sensors signal processor 5915 (preferably a digital signalprocessor (DSP)) and a payload deck signal processor 5815 (preferably adigital signal processor (DSP)). The power and auxiliary sensors signalprocessor 5915 monitors any auxiliary sensors as well as the powersource type, temperature, and available power level for each powersource 90 connected to the signal processor 5915. The payload decksignal processor 5815 monitors the power source type, temperature, andavailable power level for each power source 90 connected to the payloaddeck 80. When multiple power sources 90 are installed on the roboticvehicle 10 (i.e. on the chassis 20 and/or the payload deck 80), thepower management control logic 5410 detects via the auxiliary sensorssignal processor 5915 and the payload deck signal processor 5815 thepower source type, temperature, and available power level for each powersource 90. The auxiliary sensors signal processor 5915 and the payloaddeck signal processor 5815 each control recharging of an associatedpower source 90 based on power source type, temperature, and availablepower level for each power source 90.

FIG. 42 provides a diagram of an example robotic vehicle mission. Therobotic vehicle 10, starting from an idle state, must tow a stretcherout to a field location, wait while a casualty is loaded onto thestretcher, and then tow the stretcher and casualty back to either asecond location or back to a stating location. For both the outbound andinbound trips, the robot controller 5320 sends drive commands to thedrive modules 5500 based on an available power level, determined by thepower management logic 410 in the control logic 5400 of the robotcontroller 5320. For the outbound trip, the robot controller 5320 sendsa drive command for low-torque and high speed to quickly drive out withthe empty stretcher. For the inbound trip, the robot controller 5320sends a drive command for high-torque and low speed to slowly drive backwith the load stretcher. The ability of the amplifier commutator 5520 todeliver a dynamic power range of both amplified and reduced power to thedrive motor 5530 with a fixed gear ratio gear box 5540 allows therobotic vehicle 10 to drive quickly or slowly with low torque or hightorque.

Other robotic vehicle details and features combinable with thosedescribed herein may be found in a U.S. Provisioned filed Oct. 6, 2006,entitled “MANEUVERING ROBOTIC VEHICLES” and assigned Ser. No.60/828,611, the entire contents of which are hereby incorporated byreference.

A number of implementations of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, flippers of varied length and payload decks with other means offunctional payload attachment, such as snap-on, clamps, and magnets.Accordingly, other implementations are within the scope of the followingclaims.

1. A mobile robot comprising: a chassis defining at least one chassisvolume; first and second sets of right and left driven flippersassociated with the chassis, each flipper having a drive wheel anddefining a flipper volume adjacent to the drive wheel, the first set offlippers disposed between the second set of flippers and the chassis;motive power elements distributed among the chassis volume and theflipper volumes, the motive power elements comprising a batteryassembly, a main drive motor assembly, and a load shifting motorassembly; and a load shifting assembly pivotally attached to the chassisand comprising a load tilting motor and a load shifting motor, the loadshifting assembly defining a load shifting volume adjacent the loadtilting motor, the motive power elements being distributed among thechassis volume, the load shifting volume, and the flipper volumes,wherein the main drive motor assembly comprises a main drive motor and amain drive motor amplifier, and the load shifting motor assemblycomprises the load shifting motor and a load shifting motor amplifier.2. The mobile robot of claim 1, wherein the first set of flippers arerigidly coupled to the chassis, and the second set of flippers arerotatable 360 degrees about a pivot axis near a forward end of thechassis, the first and second of flippers having a drive axis commonwith the pivot axis.
 3. The mobile robot of claim 1, wherein eachflipper comprises a driven track, each track trained about thecorresponding drive wheel and defining the flipper volume within anenvelope defined by the track.
 4. The mobile robot of claim 1, whereinthe main drive motor amplifier and the load shifting motor amplifier aredisposed in at least one of the flipper volumes, the main drive motorand the load shifting motor are disposed in the chassis volume, and thebattery assembly is disposed in the load shifting volume.
 5. The mobilerobot of claim 1, wherein the main drive motor amplifier is disposed inat least one of the flipper volumes, the main drive motor is disposed inthe chassis volume, and the battery assembly and the load tilting motorare disposed in the load shifting volume so that the battery assemblytilts together with the load shifting assembly.
 6. The mobile robot ofclaim 1, wherein the chassis extends into the flipper volumes defined bythe first set of flippers, at least one of the flipper volumes definedby the first set of flippers housing the main drive motor amplifier, thechassis volume housing the main drive motor, and the load shiftingvolume housing the battery assembly and the load tilting motor assembly.7. The mobile robot of claim 1, wherein the shifting motor amplifier ishoused in at least one of the flipper volumes.
 8. The mobile robot ofclaim 1, wherein the load shifting assembly comprises a linkageconnecting a payload assembly to the chassis, the linkage having a firstend rotatably connected to the chassis at a first pivot, and a secondend rotatably connected to the payload assembly at a second pivot, bothof the first and second pivots including independently controllablepivot drivers operable to rotatably position their corresponding pivotsto control both fore-aft position and pitch orientation of the payloadassembly with respect to the chassis.
 9. The mobile robot of claim 8,wherein the independently controllable pivot drivers provide bothfore-aft position and pitch orientation of the payload assembly withrespect to the chassis to selectively displace a center of gravity ofthe payload assembly both forward and rearward of a center of gravity ofthe chassis.
 10. The mobile robot of claim 8, wherein the first end ofthe linkage is rotatably connected near the front of the chassis, suchthat the payload assembly is displaceable to an aft-most position inwhich the payload assembly is located within a footprint of the chassis.11. The mobile robot of claim 1, wherein a center of gravity of therobot remains within an envelope of rotation of the second set offlippers.
 12. An obstacle climbing mobile robot comprising: a chassis;first and second sets of right and left driven flippers associated withthe chassis, the first set of flippers disposed between the second setof flippers and the chassis, each flipper having a drive wheel anddefining a first volume adjacent to the drive wheel; a load shiftingassembly associated with the chassis and including a tilt motor, theload shifting assembly defining a second volume adjacent the tilt motor,the chassis defining a third volume adjacent at least one of the drivewheels; and motive power elements distributed among the first volumes,the second volume, and the third volume, the motive power elementscomprising a battery assembly, a main drive motor assembly, and a loadshifting motor assembly.
 13. The obstacle climbing mobile robot of claim12, wherein the main drive motor assembly comprises a main drive motoramplifier and a main drive motor, and the load shifting motor assemblycomprises a load shifting motor amplifier and a load shifting motor. 14.The obstacle climbing mobile robot of claim 13, wherein at least one ofthe first volumes houses the main drive motor amplifier and the loadshifting motor amplifier, the second volume houses the battery assembly,and the third volume houses the main drive motor and the load shiftingmotor.
 15. The obstacle climbing mobile robot of claim 13, wherein atleast one of the first volume houses the main drive motor amplifier, thesecond volume houses the battery assembly and the load tilting motor, sothat the battery assembly tilts together with the load shiftingassembly, and the third volume houses the main drive motor.
 16. A mobilerobot comprising: a chassis defining at least one chassis volume; firstand second sets of right and left driven flippers associated with thechassis, each flipper having a drive wheel and defining a flipper volumeadjacent to the drive wheel, the first set of flippers disposed betweenthe second set of flippers and the chassis; and motive power elementsdistributed among the chassis volume and the flipper volumes, the motivepower elements comprising a battery assembly, a main drive motorassembly, and a load shifting motor assembly; and a load shiftingassembly pivotally attached to the chassis and comprising a load tiltingmotor and a load shifting motor, the load shifting assembly defining aload shifting volume adjacent the load tilting motor, the motive powerelements being distributed among the chassis volume, the load shiftingvolume, and the flipper volumes, wherein the load shifting assemblycomprises a linkage connecting a payload assembly to the chassis, thelinkage having a first end rotatably connected to the chassis at a firstpivot, and a second end rotatably connected to the payload assembly at asecond pivot, both of the first and second pivots includingindependently controllable pivot drivers operable to rotatably positiontheir corresponding pivots to control both fore-aft position and pitchorientation of the payload assembly with respect to the chassis.
 17. Themobile robot of claim 16, wherein the independently controllable pivotdrivers provide both fore-aft position and pitch orientation of thepayload assembly with respect to the chassis to selectively displace acenter of gravity of the payload assembly both forward and rearward of acenter of gravity of the chassis.
 18. The mobile robot of claim 16,wherein the first end of the linkage is rotatably connected near thefront of the chassis, such that the payload assembly is displaceable toan aft-most position in which the payload assembly is located within afootprint of the chassis.